This application relates to radar imaging of an object.
Radar has been widely utilized in a number of applications for decades. In its traditional uses, radar has been utilized to identify a component a good distance away from the radar system. Well known examples include monitoring approaching aircraft, as an example.
More recently, near field radar imaging has been utilized, particularly in quality control applications. Near field radar imaging directs radar beams at an object, and processes the reflected signals to create an image of the component. This imaging can be utilized as quality control to check the relative surfaces of various locations on an object, or check other aspects of quality. As one example, aircraft, in particular for military applications, are often provided with a coating intended to mask radar reflectivity. Near field radar quality control imaging is often performed on such components to determine the quality of the coating, by looking at the reflectivity of various points on the coated component.
The distance between a component and the radar system impacts the signal strength. Thus, the signal strength will differ between adjacent locations on an object should the distance between the radar system and those particular points be different.
In the traditional application of monitoring a distant item, such as an approaching aircraft, these differences in distances for points on a component are so insignificant compared to the overall distance that no correction is necessary. However, in near field imaging, the different distances between closely related surfaces on a component can adversely effect the quality control information being provided by the near field radar imaging.
In the traditional application of near field imaging, a correction to the image strength is made at each point in the image based on the apparent distance between the image location and the radar antenna. This correction is referred to as the “R to the fourth” (R4) correction, as the correction depends on the fourth power of the distance between the image location and the radar antenna